Process for forming artificial rocks

ABSTRACT

A process for forming an artificial rock is provided. The process includes forming an outer mold having an outer surface and inner surface, the inner surface defining the size, shape and detail of the artificial rock to be formed. An inner mold is formed to be receivable within the outer mold. The inner mold and outer mold are secured in place relative to each other to define a space therebetween. Molding material is poured into the space between the inner mold and outer mold. The molding material is allowed to harden to form an artificial rock within the space. The molds are then separated leaving the artificial rock.

FIELD OF THE INVENTION

The present invention relates to a process for forming landscapingobjects, such as hollow rocks useful in landscaping for residences andbusinesses.

BACKGROUND OF THE INVENTION

Landscape rocks and boulders have long been used as in landscaping toprovide a natural effect and to highlight certain areas. To use actualboulders, it is necessary to find suitably shaped boulders, transportthem to the location to be used and then dig the ground around theboulder such that it rests within the ground at a suitable height. Thisprocess is obviously time consuming and burdensome. A variety ofalternatives to natural boulders have been developed.

Contemporary landscape architects utilize artificial boulders, which areactually hollowed out boulder liners or shells, having a bottom portioncut off to fit flush on the ground. Such liners are typically formed ofconcrete which is formed from a mold. The mold, in turn, is formed froman actual boulder which has been selected for its size, shape and designcharacteristics. By varying the composition or surface treatment of theboulder liner, different colors or surface characteristics can beobtained.

Though contemporary landscape boulder liners have significant functionaland economic advantages over actual boulders, the current processes forforming such landscape boulders suffer significant shortcomings whichimpede both production rate and the quality of the resulting landscapeboulders. The quality of such landscape boulders may be measured by howclosely the surface of the landscape boulder reflects the surfacedetails of the actual boulder used in the formation process.

Contemporary processes for forming landscape boulders typically usefiberglass molds made by forming a latex skin on the surface of theactual boulder, and then constructing the fiberglass mold around thelatex skin. Cement is pumped or hand troweled into the invertedfiberglass mold and allowed to set. The only force acting on the cementis its own weight. By the action of gravity, the cement generally movesdownward toward the bottom of the mold, i.e., representing the upperportion of the landscape boulder when the process is complete.Consequently, the resulting product typically does not assume allsurface characteristics of the mold. This deficiency is particularlysignificant in the upper and side portions of the inverted landscapeboulder. In order to remedy the deficiencies of the product formed bysuch processes, it is typically necessary to apply additional cement byhand to the lower outside portions of the completed landscape boulder,resulting in the addition of non-repeating detail which is only vaguelyreminiscent of the initial boulder. As will be evident from the abovedescription, such contemporary processes have significant deficiencieswith respect to both the quality of the resulting product and theproduction rate. The present invention addresses these and otherdeficiencies in the prior art as set forth below.

SUMMARY OF THE INVENTION

A process for forming an artificial rock is disclosed. The processcomprises forming an outer mold having an outer surface and innersurface, the inner surface defining the size, shape and detail of theartificial rock to be formed. An inner mold is formed to be receivablewithin the outer mold. The inner mold and outer mold are secured inplace relative to each other to define a space therebetween. Moldingmaterial is poured into the space between the inner mold and outer mold.The molding material is allowed to harden to form an artificial rockwithin the space. The molds are then separated leaving the artificialrock.

The void between the inner mold and outer mold defines the thickness ofthe resulting landscape boulder, which can be regulated by varying thesize of the inner mold, and the clearance between the inner and outermolds.

In the presently preferred embodiment, the inner mold is made by forminga hard liner on the outer mold and carving a body of foam into a moldinsert. The mold insert may further be provided with a plurality ofholes into which the molding material may flow. Molding material ispoured into the space between the hard liner and mold insert, attachingto the mold insert. Upon hardening of the molding material, the moldsare separated and the hard liner may be discarded. The inner mold isthen complete.

The outer mold may be formed by a variety of different processes. In thepresently preferred embodiment, an outer mold is formed by building adam about a actual boulder to a height defined by a molding line. Thedam is filled with molding material and allowed to harden to form theshape of the outer mold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the apparatus used to form a mold in accordancewith the present invention;

FIG. 2 is a top view of the apparatus used to form a mold in accordancewith the present invention;

FIG. 3 is a side view illustrating the outer and inner molds.

FIG. 4 is a top view illustrating the outer and inner molds.

FIG. 5 is an enlarged view of a portion of FIG. 3.

FIG. 6 is an enlarged view of a portion of FIG. 3, wherein the hardliner has been removed to provide space for the cement mixture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiment of the invention, and is not intended to represent the onlyform in which the present invention may be implemented or utilized. Thedescription sets forth the functions and sequence of steps ofconstructing a landscape boulder in connection with the illustratedembodiments. It is understood, however, that the same or equivalentprocess steps may be accomplished by different embodiments and thatobjects other than landscape boulders may be replicated in accordancewith the disclosed process. Such equivalent process steps and processproducts are also intended to be encompassed within the spirit and scopeof the invention.

The first step in the formation of landscape objects is the selection ofa rock or other object suitable for molding. Not all objects can bemolded. Rocks with deep impressions or angled undercuts may posesignificant problems upon removal of the casting. Rocks with minimalundercuts are selected and a molding line is determine prior to set up.The molding line is an imaginary plane which passes through the rockeliminating that portion of the rock which may be unsuitable for moldingdue to unacceptable undercuts and/or impressions.

As illustrated at FIG. 1 and 2, once an appropriate rock 11 is selected,the rock 11 is placed upon a support platform 13. The support platform13 supports the rock 11 and set-up material in a level position. Theplatform is preferably constructed for mobility, incorporating mountingwheels or being constructed to allow forklift use.

After the platform 13 is constructed, the rock 11 is centered on theplatform with the molding line level. The molding line 17 is typicallyabove the platform. A frame 19 is then constructed around the rock andfastened down to the platform. The depth of the frame 19 is defined bythe distance between the molding line 17 and the upper surface of thesupport platform 13. The length and width of the frame are preferablyformed to be adequate to allow 5 or 6 inches between the inside of theframe 19 and the surface of the rock 11. The void 21 between the frame19 and the rock 11 is filled with sand and packed firm to within 1-2inches of the molding line 17. This 1-2 inches is a formed concrete base23, troweled smooth and level, and allowed to dry. The concrete base 23and rock 11 are preferably both sealed with an appropriate sealer, suchas shellac, and coated with a mold release agent.

The next step in the formation of the mold is to put a sheet metal damin place. In the presently preferred embodiment, sheet metal of 26 gaugeis cut to a width that exceeds the dimension between the molding lineand the pour line. The length exceeds the circumference of the rock withan allowance of at least 1-2 inches between the rock 11 and the damwall. The sheet metal dam 25 is carefully bent around the rock 11allowing 1-2 inches for molding material. The overlap of the sheet metalmay be joined with duct tape on both sides. With the sheet metal dam 25in place, a ring of cement grout 27 is applied to the outside bottomedge with a grouting bag. The purpose of cement grout 27 is to hold thesheet metal in place and to seal the joint between the sheet metal dam25 and the concrete base 23. When the grout is dry, a release agent isapplied to the inside surface of the sheet metal.

The next step is the placement of the alignment fasteners. Alignmentfasteners 29 are later used to hold down and properly align the innermold with respect to the outer mold. In the presently preferredembodiment, the alignment fasteners 29 are steel dowels with femalethreads embedded in the surface of the outer mold. The placement of thealignment fasteners 29 is significant in that they are preferablypositioned to equalize the upwards stress on the outer mold, uniformlydistributing the stress of holding down the inner mold.

With the alignment fasteners in position, molding material is thenpoured into place. In the presently preferred embodiment, the moldingmaterial used is a polyurethane compound, two component system. However,various types of molding material may be used within the scope of theinvention. When mixed together, the molding material cures at roomtemperature to an elastomer with shore "A" hardness of 40-60. When themolding material has dried, the resulting mold, i.e., outer mold 31, isremoved from the rock and placed upright with the impression facing up.

Referring to FIGS. 3 and 4, the next step in the process is theformation of a hard liner 37 on the inside surface of the outer mold 31.As described below, once the mold is complete, it will function toreproduce products which are substantially replicas of the hard liner37. To form the hard liner, cement or other similar materials is handtrolled on the inner surface of the outer mold. The thickness of themixture depends upon the size of the rock to be produced and thestrength desired, typically between 3/4 and 3 inches thick. The insidesurface of the hard liner 37 is typically formed to have a smooth bowlshape. A sealer and release agent are then applied to the exposedsurface of the hard liner as described above.

Next, a foam insert is then placed within the outer mold. The insert 39is formed of a rigid polyurethane foam, carved and shaped tosubstantially fill the space of the hard liner, leaving approximately1/2 to 1 inch of space between the rigid foam and the hard liner on allsides. The space remaining between the hard liner 37 and foam insert isfilled with liquid molding material 40, as described below. 1/2 to 1inch holes 41 are preferably drilled through the foam in all directions,particularly where the alignment brackets touch the foam. This procedureprevents the hardened molding material from pulling away from the foaminsert during mold separation.

Alignment brackets 33 are used to hold down and properly align the foaminsert 39 to the outer mold. The alignment brackets may be formed ofwood, metals or plastic and is formed to be of size and strengthsufficient to hold the inner mold without bowing under stress created bybuoyancy during the casting process. The brackets 33 are centered overthe alignment fasteners 29, with holes marked and drilled for an anchorbolt. The brackets are preferably marked and cut to fit the outside edgeof the outer mold. With the brackets 33 in place, the center of eachbracket is identified and marked. At each mark, a hole is drilled toattach a 3/8 or 1/2 inch eyebolt 35. The eyebolt is used to pull up onwhen separating the inner mold from the casting.

Molding material 40, such as polyurethane, is then poured into the spacebetween the hard liner and the foam insert. Once half poured, thebuoyancy of the foam insert upon the molding material will typicallyurge the foam upwards against the alignment brackets. The foam insertmay then be manually manipulated in order to provide circumferentialclearance between the foam insert and the hard liner. The pouring isthen completed. When the molding material 40 is dried, the foam insertincased in molding material now attached thereto, is separated from thehard liner. The hardened molding material 40 and foam insert 39collectively become the inner mold. The hard liner may then be separatedfrom the outer mold and discarded or may be used as a landscape boulder.

In the production of landscape boulders, as shown at FIG. 6, the outerand inner molds are again mated and the cement mixture is poured intothe intermediate space 42 previously occupied by the hard liner. Afterthe cement mixture hardens, the outer and inner molds are separated,leaving a landscape boulder. This process is then repeated to makeadditional landscape boulders.

The use of the inner mold to form the landscape boulder substantiallyequalizes and provides a means to effectively regulate the thickness ofthe landscape boulder around its entire surface area. Though variationsin such thickness may occur as a consequence of the irregularity of thedesired surface, the landscape boulder may be formed so that allportions of the landscape boulder have a minimum thickness withoutrequiring an excess of cement mixture or other molding material.Moreover, the use of the inner mold provides a further advantage thatthe cement mixture is urged against the side walls of the mold to agreater degree than that resulting from contemporary process of simplypumping or shooting casting material into the mold. As a consequence,products formed in accordance with the present invention can obtainsignificantly greater detail on a repeatable basis, substantiallyeliminating the need for any hand troweling of the product after it iswithdrawn from the mold. Consequently, the production rate that can beachieved by use of the present inventive process is significantlygreater than that achieved by contemporary processes.

As will be apparent to those of ordinary skill in the art, the presentinvention has application beyond merely the reproduction of landscapeboulders. Other types of landscape objects, such as objects fordecorating pools or buildings may be reproduced in accordance with thesame process as described above. Accordingly, the present invention isnot intended to be limited to the particular types of objects beingreproduced.

As will further be apparent to those of ordinary skill in the art, theprocess may be modified or supplemented to provide various types ofsurface coloring or detail. For example, a more granular surface may beprovided by spray application of commercially available surface finishproducts. Coloring finishes may also be applied in accordance withtechniques well-known in the art to those of ordinary skill in the art.

It should also be recognized that various aspects of the presentinvention may be implemented in conjunction with inner and/or outermolds formed in accordance with different methods or construction.Accordingly, the description of the presently preferred embodiments ofthe overall process, described above, are not intended to be limiting ofthe particular combination of process steps which constitute the presentinvention.

What is claimed is:
 1. A process of forming a mold useful in theproduction of artificial rocks comprising:forming an outer mold, saidmold having an outer surface and an inner surface, said inner surfacedefining the size, shape and detail of the artificial rock; forming ahard liner upon the inner surface of the outer mold; forming a moldinsert receivable within the hard liner; securing said mold insert andhard liner in place relative to each other to define a space between themold insert and the hard liner; pouring molding material into the spacebetween the mold insert and the hard liner; allowing the moldingmaterial to harden; separating the outer mold from the mold insert andattached molding material, the mold insert and attached molding materialcollectively forming an inner mold; and separating the hard liner fromthe outer mold.
 2. The process as recited in claim 1 wherein the step ofpouring molding material into the space between the mold insert and hardliner comprises filling the space with urethane.
 3. The process asrecited in claim 1 further comprising the step of regulating thethickness of the mold by varying the size and shape of the hard liner.4. The process as recited in claim 1 wherein the step of forming a moldinsert comprises carving a body of foam to have a shape substantiallyconforming to the hard liner inner surface.
 5. The process as recited inclaim 4 wherein the step of forming a mold insert further comprises thestep of forming a plurality of holes through the insert into whichmolding material may flow.
 6. The processes recited in claim 1 whereinthe hard liner is formed to have a substantially uniform thickness. 7.The process as recited in claim 1 wherein the step of securing the moldinsert and outer mold in place comprises the step of engaging uppersurfaces of the mold insert and the outer mold by at least one fasteningmember.
 8. The process as recited in claim 1 wherein said step offorming an outer mold comprises:disposing a natural rock to bereproduced on a platform; defining a molding line about the naturalrock; forming a dam about the rock to a level defined by the moldingline; filling the dam with molding material; and allowing the moldingmaterial to harden to form the outer mold.
 9. A process of formingartificial rocks comprising:forming an outer mold, said mold having anouter surface and an inner surface, said inner surface defining thesize, shape and detail of the artificial rock; forming a hard liner uponthe inner surface of the outer mold; forming a mold insert receivablewithin the hard liner; securing said mold insert and outer mold in placerelative to each other to define a space between the outer mold and themold insert; pouring molding material into the space between the moldinsert and the hard liner; allowing the molding material to harden;separating the outer mold from the mold insert and attached moldingmaterial, the mold insert and attached material collectively forming aninner mold; separating the hard liner from the outer mold; joining theinner mold and outer mold together; pouring molding material into thespace between the inner and outer mold and allowing the material toharden; and separating the inner and outer mold to release an artificialrock.
 10. The process as recited in claim 9 wherein the step of pouringmolding material into the space between the mold insert and hard linercomprises filling the space with urethane molding material.
 11. Theprocess as recited in claim 9 further comprising the step of regulatingthe thickness of the artificial rock by varying the size and shape thehard liner.
 12. The process as recited in claim 9 wherein the step offorming a mold insert comprises carving a body of foam to have a shapesubstantially conforming to the inner surface of the hard liner.
 13. Theprocess as recited in claim 9 wherein the step of forming an artificialrock further comprises the step of forming a plurality of holes throughthe insert into which molding material may flow.
 14. The processesrecited in claim 9 wherein the hard liner is formed to have asubstantially uniform thickness.
 15. The process as recited in claim 9wherein the step of securing the mold insert and outer mold in placecomprises the step of engaging upper surfaces of the mold insert and theouter mold by at least one fastening member.
 16. The process as recitedin claim 10 wherein said step of forming an outer moldcomprises:disposing a natural rock to be reproduced on a platform;defining a molding line about the natural rock; forming a dam about theobject to a level defined by the molding line; filling the dam withmolding material; and allowing the molding material to harden to formthe outer mold.